2,153 research outputs found
Improving Agricultural Irrigation on the Balkhab River, Afghanistan
In Afghanistan, where 80% of the population is rural, irrigated agriculture is important for satisfying subsistence needs. While most of the irrigated agriculture is fed by diversion canal systems which tap surface flows, legal and physical water infrastructure in the region is generally poor. A math programming model is used to optimize irrigation strategies under different water-availability and policy scenarios. It is found that the construction of a reservoir could increase net revenues to a representative farming community by up to 30%. However, even greater benefits may result from increasing distribution efficiencies, depending on the initial level of conveyance losses. Further, property rights schemes may be implemented to distribute wealth more evenly through various zones at minimal cost to the agricultural community as a whole. These results may prove useful to policymakers or water authorities in reestablishing water rights.linear programming, irrigation, Afghanistan, Agricultural and Food Policy, Community/Rural/Urban Development, International Development,
Novel use of stir bar sorptive extraction (SBSE) as a tool for isolation of oviposition site attractants for gravid Culex quinquefasciatus
Mosquitoes such as Culex quinquefasciatus Say (Diptera: Culicidae) are important vectors of organisms that cause disease in humans. Research into the development of effective standardized odour baits for blood-fed females (oviposition attractants), to enable entomological monitoring of vector populations, is hampered by complex protocols for extraction of physiologically active volatile chemicals from natural breeding site water samples, which have produced inconsistent results. Air entrainment and solvent extraction are technically demanding methods and are impractical for use in resource poor environments where mosquito-borne disease is most prevalent. This study reports the first use of a simple, robust extraction technique, stir bar sorptive extraction (SBSE), to extract behaviourally active small lipophilic molecules (SLMs) present in water samples collected from Cx. quinquefasciatus breeding sites in Tanzania. Extracts from a pit latrine and from a cess pool breeding site attracted more gravid Cx. quinquefasciatus in pair choice bioassays than control extracts, and coupled gas chromatography-electroantennography (GC-EAG) allowed tentative identification of 15 electrophysiologically active chemicals, including the known oviposition attractant, skatole (3-methylindole). Here, we have demonstrated, using simple pair choice bioassays in controlled laboratory conditions, that SBSE is effective for the extraction of behaviourally and electrophysiologically active semiochemicals from mosquito breeding site waters. Further research is required to confirm that SBSE is an appropriate technique for use in field surveys in the search for oviposition cues for Cx. quinquefasciatus
Atomic and Molecular Opacities for Brown Dwarf and Giant Planet Atmospheres
We present a comprehensive description of the theory and practice of opacity
calculations from the infrared to the ultraviolet needed to generate models of
the atmospheres of brown dwarfs and extrasolar giant planets. Methods for using
existing line lists and spectroscopic databases in disparate formats are
presented and plots of the resulting absorptive opacities versus wavelength for
the most important molecules and atoms at representative temperature/pressure
points are provided. Electronic, ro-vibrational, bound-free, bound-bound,
free-free, and collision-induced transitions and monochromatic opacities are
derived, discussed, and analyzed. The species addressed include the alkali
metals, iron, heavy metal oxides, metal hydrides, , , , ,
, , , and representative grains. [Abridged]Comment: 28 pages of text, plus 22 figures, accepted to the Astrophysical
Journal Supplement Series, replaced with more compact emulateapj versio
Real-Time Sequential Conic Optimization for Multi-Phase Rocket Landing Guidance
We introduce a multi-phase rocket landing guidance framework that can handle
nonlinear dynamics and does not mandate any additional mixed-integer or
nonconvex constraints to handle discrete temporal events/switching. To achieve
this, we first introduce sequential conic optimization (SeCO), a new paradigm
for solving nonconvex optimal control problems that is entirely devoid of
matrix factorizations and inversions. This framework combines sequential convex
programming (SCP) and first-order conic optimization and can solve unified
multi-phase trajectory optimization problems in real-time. The novel features
of this framework are: (1) time-interval dilation, which enables multi-phase
trajectory optimization with free-transition-time; (2) single-crossing compound
state-triggered constraints, which are entirely convex if the trigger and
constraint conditions are convex; (3) virtual state, which is a new approach to
handling artificial infeasibility in SCP methods that preserves the shapes of
the constraint sets; and, (4) the use of the proportional-integral projected
gradient method (PIPG), a high-performance first-order conic optimization
solver, in tandem with the penalized trust region (PTR) SCP algorithm. We
demonstrate the efficacy and real-time capability of SeCO by solving a relevant
multi-phase rocket landing guidance problem with nonlinear dynamics and convex
constraints only, and observe that our solver is 2.7 times faster than a
state-of-the-art convex optimization solver
Considering the role of cognitive control in expert performance
© 2014, Springer Science+Business Media Dordrecht. Dreyfus and Dreyfus’ (1986) influential phenomenological analysis of skill acquisition proposes that expert performance is guided by non-cognitive responses which are fast, effortless and apparently intuitive in nature. Although this model has been criticised (e.g., by Breivik Journal of Philosophy of Sport, 34, 116–134 2007, Journal of the Philosophy of Sport, 40, 85–106 2013; Eriksen 2010; Montero Inquiry:An interdisciplinary Journal of Philosophy, 53, 105–122 2010; Montero and Evans 2011) for over-emphasising the role that intuition plays in facilitating skilled performance, it does recognise that on occasions (e.g., when performance goes awry for some reason) a form of ‘detached deliberative rationality’ may be used by experts to improve their performance. However, Dreyfus and Dreyfus (1986) see no role for calculative problem solving or deliberation (i.e., drawing on rules or mental representations) when performance is going well. In the current paper, we draw on empirical evidence, insights from athletes, and phenomenological description to argue that ‘continuous improvement’ (i.e., the phenomenon whereby certain skilled performers appear to be capable of increasing their proficiency even though they are already experts; Toner and Moran 2014) among experts is mediated by cognitive (or executive) control in three distinct sporting situations (i.e., in training, during pre-performance routines, and while engaged in on-line skill execution). We conclude by arguing that Sutton et al. Journal of the British Society for Phenomenology, 42, 78–103 (2011) ‘applying intelligence to the reflexes’ (AIR) approach may help to elucidate the process by which expert performers achieve continuous improvement through analytical/mindful behaviour during training and competition
The Structure of Pre-transitional Protoplanetary Disks I: Radiative Transfer Modeling of the Disk+Cavity in the PDS 70 system
Through detailed radiative transfer modeling, we present a disk+cavity model
to simultaneously explain both the SED and Subaru H-band polarized light
imaging for the pre-transitional protoplanetary disk PDS 70. Particularly, we
are able to match not only the radial dependence, but also the absolute scale,
of the surface brightness of the scattered light. Our disk model has a cavity
65 AU in radius, which is heavily depleted of sub-micron-sized dust grains, and
a small residual inner disk which produces a weak but still optically thick NIR
excess in the SED. To explain the contrast of the cavity edge in the Subaru
image, a factor of ~1000 depletion for the sub-micron-sized dust inside the
cavity is required. The total dust mass of the disk may be on the order of 1e-4
M_sun, only weakly constrained due to the lack of long wavelength observations
and the uncertainties in the dust model. The scale height of the
sub-micron-sized dust is ~6 AU at the cavity edge, and the cavity wall is
optically thick in the vertical direction at H-band. PDS 70 is not a member of
the class of (pre-)transitional disks identified by Dong et al. (2012), whose
members only show evidence of the cavity in the millimeter-sized dust but not
the sub-micron-sized dust in resolved images. The two classes of
(pre-)transitional disks may form through different mechanisms, or they may
just be at different evolution stages in the disk clearing process.Comment: 28 pages (single column), 7 figures, 1 table, ApJ accepte
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Cardiovascular Risk Factors and Masked Hypertension: The Jackson Heart Study
Masked hypertension is associated with increased risk for cardiovascular disease. Identifying modifiable risk factors for masked hypertension could provide approaches to reduce its prevalence. Life’s Simple 7 is a measure of cardiovascular health developed by the American Heart Association that includes body mass index, physical activity, diet, cigarette smoking, blood pressure (BP), cholesterol, and glucose. We examined the association between cardiovascular health and masked daytime hypertension in the Jackson Heart Study, an exclusively African American cohort. Life’s Simple 7 factors were assessed during a study visit and categorized as poor, intermediate, or ideal. Ambulatory BP monitoring was performed after the study visit. Using BP measured between 10:00 AM and 8:00 PM on ambulatory BP monitoring, masked daytime hypertension was defined as mean clinic systolic BP/diastolic BP <140/90 mm Hg and mean daytime systolic BP/diastolic BP ≥135/85 mm Hg. Among the 758 participants with systolic BP/diastolic BP <140/90 mm Hg, 30.5% had masked daytime hypertension. The multivariable-adjusted prevalence ratios for masked daytime hypertension comparing participants with 2, 3, and ≥4 versus ≤1 ideal Life’s Simple 7 factors were 0.99 (95% confidence interval [CI], 0.74–1.33), 0.77 (95% CI, 0.57–1.03), and 0.51 (95% CI, 0.33–0.79), respectively. Masked daytime hypertension was less common among participants with ideal versus poor levels of physical activity (ratio, 0.74; 95% CI, 0.56–1.00), ideal or intermediate levels pooled together versus poor diet (prevalence ratio, 0.73; 95% CI, 0.58–0.91), ideal versus poor levels of cigarette smoking (prevalence ratio, 0.61; 95% CI, 0.46–0.82), and ideal versus intermediate levels of clinic BP (prevalence ratio, 0.28, 95% CI, 0.16–0.48). Better cardiovascular health is associated with a lower preva lence of masked hypertension
Effective intra-S checkpoint responses to UVC in primary human melanocytes and melanoma cell lines
The objective of this study was to assess potential functional attenuation or inactivation of the intra-S checkpoint during melanoma development. Proliferating cultures of skin melanocytes, fibroblasts and melanoma cell lines were exposed to increasing fluences of UVC and intra-S checkpoint responses were quantified. Melanocytes displayed stereotypic intra-S checkpoint responses to UVC qualitatively and quantitatively equivalent to those previously demonstrated in skin fibroblasts. In comparison to fibroblasts, primary melanocytes displayed reduced UVC-induced inhibition of DNA strand growth and enhanced degradation of p21Waf1 after UVC, suggestive of enhanced bypass of UVC-induced DNA photoproducts. All nine melanoma cell lines examined, including those with activating mutations in BRAF or and NRAS oncogenes, also displayed proficiency in activation of the intra-S checkpoint in response to UVC irradiation. The results indicate that bypass of oncogene-induced senescence during melanoma development was not associated with inactivation of the intra-S checkpoint response to UVC-induced DNA replication stress
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